This invention pertains to magnetic recording and more particularly to the magnetic recording of bits by different width pulses.
There have recently become available inexpensive magnetic tape cassette-systems where the speed of the tape past the read/record head can vary over considerable limits. In order to make the interpretation of the data selfclocking there has been proposed a recording scheme wherein in effect the width of the pulse within a bit cell represents the data bit, i.e., if the cell or element has one width it represents a binary one and if it has another width it represents a binary zero. This representation is disclosed in U.S. Pat. Nos. 2,887,674 and 3,720,927. While the former patent shows the generation of such a waveform it is speed sensitive since data recovery relies on sampling utilizing fixed and invarient time intervals which cannot be changed even if the speed of the tape changes.
On the other hand, U.S. Pat. No. 3,720,927 teaches a substantially speed insensitive system since the data is interpreted by utilizing the ratio of the time between the start of the data cell and the transition between states of magnetization and the time between the transition and the end of the data cell. However, this latter patent can only reliably distinguish between the two possible bits as long as the bits are not too closely packed.